The present invention relates to an apparatus for reducing the size of, and/or for mixing, solid, pasty and/or liquid material. The apparatus includes a cylindrical housing that is preferably disposed in a vertical position. Disposed in the housing is at least one grinding roller, which cooperates with the inner surface of the housing. Each grinding roller is mounted between two bearing disks in such a way as to be rotatable about its central axis and eccentrically relative to the central axis of the housing. The bearing disks in turn are rotatably driven about the central axis of the housing.
Apparatus of this general type, which are also known as roll or planetary mills or grinders, are known in various forms. The peripheral surfaces of their grinding rollers press the material that is to be reduced in size or mixed against the inner surface of the housing. These grinding rollers must be in the position to move inwardly when pieces of material that are too hard or too large pass through in order to avoid undue stress or even destruction.
With one heretofore known embodiment, as disclosed in Swiss Patent No. 158 018, to provide for this inward movement the grinding rollers are resiliently embodied, for example in the manner of a helical spring. A helical spring also forms the grinding roller body in German Offenlegungsschrift No. 2,542 109, which furthermore provides the possibility for adjustment in the radial direction by having its central axis formed from a flexible wire cable.
The drawback of these heretofore known apparatus is that the mobility of the grinding rollers that operate along the inner surface of the housing cannot be limited to a movement that is radial relative to the central axis of the housing. On the contrary, such movements include displacement of the central axes of the grinding rollers in the circumferential direction, i.e. in the direction of movement of the grinding rollers. This leads to pivoting movements of the grinding rollers in the direction of their circular path, which in turn leads to great wear of the inner surface of the housing and of the surface of the grinding rollers.
Furthermore, these pivoting movements result in unforeseeably great axial forces in the mounting of the grinding rollers. As a result of the high speeds involved, these axial forces cannot be overcome very well, and in a short period of time destroy the mountings for the grinding rollers.
Proceeding from an apparatus of the aforementioned general type, it is an object of the present invention, while avoiding the aforementioned drawbacks, to provide an arrangement and mounting of the grinding rollers that, while providing a straightforward construction and great functional reliability, makes it possible for the grinding rollers to deflect radially, yet avoids the generation of unduly great axial mounting or bearing forces.